Astronomical events for Indian observers SkyNews September 2019

About SkyNews: List of Events SkyNews is a monthly compendium of astronomy Dt Dy Time Event events observable from India; it is primarily meant for 02 Mo 15:48 Mars Conj. astronomy enthusiasts and amateur astronomers. 04 We 06:56 Mercury Superior Conj. Most of the events listed here can be observed by the 06 Fr 08:40 First Quarter naked eye. Some interesting events are observable 06 Fr 12:22 Moon-Jupiter: 2.4° S through a pair of binoculars or a small telescope. 08 Su 15:09 Moon South Dec.: 22.5° SkyNews will regularly carry the following sections: 08 Su 19:23 Moon-Saturn: 0° 1) Visibility of Planets: The planets visible in the night 08 Su 23:05 Moon Descending Node sky during the month will be identified. Their 10 Tu 11:48 Neptune Opposition positions will be given with respect to the 13 Fr 19:02 Moon Apogee: 406400 km constellation in which they appear. The date of transit from one constellation to other is based on the 14 Sa 10:03 Full Moon boundaries of the constellations as defined by the 20 Fr 09:30 Mercury max E 24.6° International Astronomical Union. 20 Fr 21:44 Moon-Aldebaran: 2.8° S 2) March of the Moon: An easy way to identify a star or 22 Su 08:11 Last Quarter a planet with the Moon as a reference. 23 Mo 07:24 Moon North Dec.: 22.7° 3) List of Events: Positions and phases of the Moon, conjunctions, occultations, etc. 23 Mo 12:00 Moon Ascending Node 4) Notes on Events: Any extra information about a 23 Mo 13:19 Autumnal Equinox celestial event. 25 We 02:45 Moon-Beehive: 0.4° S SkyNews will also carry notes on interesting events like 28 Sa 07:57 Moon Perigee: 357800 km equinoxes; practical tips for night sky observation; basic 28 Sa 23:56 New Moon calculations that can be done by amateur astronomers; 29 Su 09:43 Mercury-Spica: 1.3° N and simple experiments that can be done from a school ground or a building terrace. ------~~~ ------Antares (α Scorpii or Jyeshtha). The next day on 6 Sun and Planets: September it is less than 4° from Jupiter. It is also the first quarter and the Moon will be close to the celestial Mercury, Venus and Mars are not quite favourable for meridian at sunset. observation this month. They are too close to the Sun to observe safely (i.e. without hurting your eyes). The celestial meridian is an imaginary line passing from the north celestial pole through the observer's zenith to The Sun, Mercury, Venus and Mars are in Leo, the Lion the south celestial pole. (Simha) in the beginning of the month and move into Virgo, the Virgin (Kanya) on 17, 10, 9 and 24 On 8 September the Moon is less than a degree away September respectively. from Saturn. On this day the Moon will occult Saturn. This event is not visible over India. Jupiter is in Ophiuchus, the Serpent Bearer (Bhujangadhari or Sarpdhar); and Saturn is in Full moon is on 14 September. Late in the night on 20 Sagittarius, the Archer, this month. September, the waning Moon, nearly 64% illuminated, can be seen next to Aldebaran (α Tauri or Rohini). The ------~~~ ------Moon enters last quarter on 22 September. On this day March of the Moon: the half illuminated moon will be close to the meridian at sunrise. The Moon can be seen in the evening sky in the beginning of the month. On 2 September, the Moon On 25 September the Moon will rise about three hours passes within 6.5° N of Spica (α Virginis or Chitra). On before the Sun and will pass less than a degree away 5 September it makes a nice triangle with Jupiter and from the open cluster M44, the Beehive Cluster. The cluster is also known as Praesepe. Less than 2° south of One can confirm these facts easily by checking the sunset and the Moon one can spot a 4th magnitude star, δ Cancri or sunrise times published in the newspapers and almanacs, or Asellus Australis This star is less than 5’ north of the by downloading almanac generating apps. ecliptic. This star is known as Pushya Nakshatra in Indian astronomy. Observe Uranus: The mornings of 25 and 26 September offer good view Uranus was the first planet to be discovered through a of the thin lunar crescent passing north of Regulus telescope by Sir William Herschel who announced its discovery on 13 March 1781. The brightness of the planet is (Magha). just at the limits of naked eye visibility. This month its For the September star map visit ASI – POEC link magnitude is 5.7. But of course, it can be easily spotted using http://astron-soc.in/outreach/resources/sky-maps/ a pair of binoculars. Uranus is in the constellation Aries that ------~~~ ------rises about an hour after the local sunset. Use the star chart given below to find Uranus and then follow September Equinox: its changing positions over the month. On 23 September, the Sun crosses the celestial equator from The faintest star on the map has magnitude 6.0. α Arietis is a north to south. On this day the Sun's rays fall perpendicular star named Hamal (2.0 mag);  Arietis is Sheratan (2.6 mag); on the equator of the Earth. The day marks the Autumnal and γ Arietis is Mesarthim, a beautiful binary star for small Equinox in the northern hemisphere. telescopes, separated by 7.6 arcsec with a combined The other time that the Sun's rays fall perpendicular on the magnitude of 3.9. The individual magnitudes of the stars are equator is around 20 March. On this day, the Sun crosses the 4.58 and 4.64; with some experience, one can make out the celestial equator from south to north, as it moves northward. 0.06 mag difference. This is called the Vernal Equinox. γ Arietis and  Arietis make Ashwin Nakshatra. It has been taught and generally believed that on the day of an equinox the hours of day and night are of equal duration. The reason given is that on this day the Sun's rays fall perpendicular to the axis of the Earth. This is quite true indeed. Yet, nowhere on the Earth are the duration of day and night equal on an equinox. There are two reasons why the duration of day and night is not equal on an equinox. One is that the Earth is a spherical body; therefore, even though the Sun's rays fall perpendicular to the equator on an equinox, at other places the rays fall at slanting angles. And, therefore, the sunrise and sunset times differ from one latitude to the other. Secondly, the Sun is not a point source of light. It has an appreciably large size of about half a degree. The time of sunrise is calculated when its upper edge (or limb, as one Uranus is just about 10.5° south of α Arietis. Star hop using a would say in astronomy) is seen above the horizon and the pair of binoculars (field of view ~ 5°) as follows: from α Ari end of day is defined as the moment when the last rays of the go south to reach the equilateral triangle of ,  and 15 Ari. Sun disappear. The base of this triangle is about 1.8°. Go further 4° south to reach the 5.72 mag star 19 Ari, which is just about as bright There is a further complication. Because of the bending of as Uranus, which is further south east of this star. You will light rays in the Earth's atmosphere due to a phenomenon notice that planet Uranus looks different from 19 Ari. Uranus called refraction, the Sun's rays close to the horizon are seen is more like a dot with a slight bluish tinge and does not a few minutes ahead or later of the 'true' sunrise or sunset twinkle. respectively. Positions of Uranus are marked for 1and 30 September. The cumulative effect of these factors is that during an equinox the daylight hours are about 7–8 minutes longer than the dark hours. This difference is much higher near and at the These pages are contributed by poles. At the poles the rays are almost parallel to the horizon; Arvind Paranjpye ([email protected]) therefore there will be 24 hours daylight at both the poles. (http://arvindparanjpye.blogspot.com/ ) and Anjanee Rao ([email protected]) Interestingly, the hours of daylight are always longer than the dark hours by about 14 minutes all through the year at the Acknowledgements: equator. http://www.lunar-occultations.com/iota/occult4.htm by Dave Herald for International Occultation Timing Association. There are indeed days when daylight hours equal dark hours. Such days are different for different latitudes. For example https://eclipse.gsfc.nasa.gov/SKYCAL/SKYCAL.html by Fred Espenak and Sumit Dutta. people on the latitudes of Delhi (~28° N) and Chennai (~13° N) will have equal day and night on 16 and 12 March Graphics using GNU Image Manipulation Program (GIMP) a cross- respectively. They will have the same again on 27 September platform image editor. and 2 October respectively. https://www.gimp.org/